Allegedly, Annes heart was torn out after execution & Henry secretly kept it in a heart-shaped casket in a church alcove in Suffolk. Is this true?
I've never heard of Anne's heart being kept by Henry but I think the legend that you're referring to is the Salle Church legend. The Reepham Benefice website, of which Salle Church is a member quotes the 1858, ‘Notes and Queries’, written by B. B. Wiffen (page 119) as saying:-
“It is said in Mrs. Strickland’s ‘Queen’s of England’ (Volume 4, page 203), that there is a tradition in Salle in Norfolk that the remains of Anne Boleyn were removed from the Tower and interred at midnight, with the rites of Christian burial, in Salle Church, and that a plain black stone without any inscription is supposed to indicate the place where she is buried. Sharon Turner, in ‘History of the Reign of King Henry VIII, volume 2, page 264, cites the following passage from Crispin’s account of Anne Boleyn’s execution, written 14 days after her death:
“Her ladies immediately took up her head and the body. They seemed without souls, they were so languid and extremely weak, but fearing that their mistress might be handled unworthily by inhuman men, they forced themselves to do this duty; and though almost dead, at last carried off her dead body wrapt in a white covering”.
You can read more about this in my article at https://www.theanneboleynfiles.com/where-is-anne-boleyn-buried/4891/